instantaneous snapshot
DESCRIPTION
What to look for when reviewing a Mixing Zone Study in WA. EPA Mixing Zone Webinar Workshop Series January 22-24, 2013. Time average image. Instantaneous snapshot. Based on: Phil Roberts, Georgia Tech, 2003. Anise Ahmed, Ph.D., P.E. How dilution is defined in WA?. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/1.jpg)
Instantaneous snapshot Time average image Based on: Phil Roberts, Georgia Tech, 2003
What to look for when reviewing a Mixing Zone Study in WA EPA Mixing Zone Webinar Workshop Series
January 22-24, 2013
Anise Ahmed, Ph.D., P.E.
![Page 2: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/2.jpg)
Volumetric Dilution factor:
Concentration based dilution factor:
How dilution is defined in WA?
CaCpCaCeDF
e
ea
VVVDF
CpCeDF
e
a
VV
![Page 3: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/3.jpg)
• Apply AKART prior to mixing zone authorization • Maximum size of mixing zone• Minimize mixing zones• Must prove no environmental harm• Consider critical conditions
Mixing Zones in WA (WAC-173-201A-400)
![Page 4: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/4.jpg)
Other Mixing zone regulations
Overlapping mixing zones Extended mixing zones Mixing zones for stormwater Mixing zones for CSOs
![Page 5: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/5.jpg)
Mixing zones and 303(d) listing
Cannot authorize discharge that contributes to an impairment
Mixing zone may be authorized if no impairment is found at the point of discharge
Discharge OK
Discharge generally not OK
OK if no further impairment of downstream listing 303d listing
![Page 6: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/6.jpg)
Mixing Zone Models used in WA
Theoretical Models• Visual PLUMES (UM3, VSW, etc.)• RIVPLUME• CFD (being reviewed)
Empirical Models• RSB (NRFIELD)
Semi-Empirical• CORMIX
![Page 7: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/7.jpg)
Farfield Predictions
Method of Brooksε =α L n
ε = lateral dispersion characteristics, m2s-1 L = length scale, m α = dispersion coefficient for Brooks algorithm (units dependent on n) n = Brook’s law exponent = 4/3 (Oceans) = 1 (Coastal and estuarine areas) = 0 (rivers)
![Page 8: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/8.jpg)
Spreadsheet for estimating far-field dilution : http://www.ecy.wa.gov/programs/eap/pwspread/pwspread.html
![Page 9: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/9.jpg)
http://www.ecy.wa.gov/programs/eap/mixzone/mixzone.html
The End
Mixing Zones Guidance in WA
![Page 10: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/10.jpg)
AKART
All known, available, and reasonable treatment Similar to BAT but more restrictive, i.e. requires
current reasonable technology Dilution only allowed after AKART
![Page 11: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/11.jpg)
Maximum Size: Streams
Hydraulic Limitation Can use only max stream flow of 25% 7Q10
Distance Limitation
Chronic Zone =300 feet + d
Acute Zone = 10% of Chronic
25%W
diffuser
W
d = depth of diffuser at 7Q10W = width of stream at 7Q10
NPDES
NPDES
QQQDF 107*25.0
max
100 ft
![Page 12: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/12.jpg)
Maximum Size: Estuaries
Distance Limitations
W = width of waterway
Chronic Zone = 400 feet + 2d
Acute Zone = 10% of Chronic
d = depth of diffuser at MLLWW = width of waterway at MLLW
(not to exceed 25% of W)
Ebb Flood
![Page 13: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/13.jpg)
Maximum Size: Oceans
Distance Limitations
Chronic Zone = 600 feet + 2d
Acute Zone = 10% of Chronic
d = depth of diffuser at MLLW
Ebb Flood
![Page 14: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/14.jpg)
Maximum Size: Lakes/Reservoirs (>15 days detention)
Mixing zones not allowed unless: All other options are exhausted Overriding public interest Advanced waste treatment is provided
If Allowed: Cannot use more than 10% of waterbody
volume Cannot use more than 10% of surface area Cannot use more than 15% of width of
waterbody.
![Page 15: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/15.jpg)
Minimize Mixing Zones
Where possible Use less than 25% 7Q10 ambient flow Use less than 25% stream width Use smaller mixing zones: < 300 feet for streams; < 200 feet for
estuaries; < 300 feet for oceans
50 100 150 200 250 300 35014
16
18
20
22
24
26
28
30
8
9
10
11
12
13
14
15
16
17
18D.Fplume width, ftplume width allowed, ft
Distance from outfall, ft
Chr
onic
dilu
tion
fact
or
plum
e w
idth
, ft
![Page 16: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/16.jpg)
No environmental harm
No loss of sensitive or important habitat, No interference with existing or
characteristic uses of the waterbody No resulting damage to the ecosystem No adverse public health affect
![Page 17: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/17.jpg)
Critical Conditions Flow and Concentration
Ambient flow Effluent flow Ambient/Effluent concentrations
Depth Stratification Dilution type
![Page 18: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/18.jpg)
Ambient Flow
Freshwater– Acute and Chronic …… 7Q10– Carcinogen ……………… Harmonic Flow– Non-Carcinogen ……… 7Q10
Saltwater– Acute …… 10th % or 90th % current velocity*– Chronic/ ……………… 50th % current
velocity*Carcinogen/Non-Carcinogen
* Evaluated over a spring and neap tide
![Page 19: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/19.jpg)
Effluent Flow
Acute … highest daily Qmax in last 3 years Chronic/Non-Carcinogens … highest monthly Qavg
in last 3 years Carcinogens … Annual Average Flow Stormwater (Western WA):
– Acute …… 1-hour peak flow from 2-yr 6-hr storm event– Chronic ..... Average flow from 2-yr 72-hr storm event
Intermittent flow: – Estimate DF using Qmax – Increase DF by (Q1-hr avg/Qmax) for acute– Increase DF by (Q4-day avg/Qmax) for chronic
![Page 20: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/20.jpg)
For Estimating Volumetric Dilution Factor
Ambient Concentration:– Assume zero when no reflux– If reflux is present use reflux as ambient
Effluent Concentration: – Assume 100% or 100 ppm
![Page 21: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/21.jpg)
For Reasonable Potential Calculation
Ambient concentration (Ca)– Acute/Chronic …. 90th percentile– Carcinogen/Non-Carcinogen…Geometric Mean
Effluent concentration (Ce)– (Acute/Chronic): Cmax x F*– (Carcinogen/Non-Carcinogen): 50th percentile
* uncertainty factor => based on number of samples, CV, and confidence interval (EPA, TSD, Table 3-1, 3-2)
ae
p CDFDF
CC *)11(
![Page 22: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/22.jpg)
Depth Freshwater
– Acute and Chronic …… at 7Q10– Carcinogen ……………… at Harmonic
Flow– Non-Carcinogen ……… at 7Q10
Tidally influenced Freshwater– Same as above but at MLLW
Marine waters– At MLLW
![Page 23: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/23.jpg)
Stratification Use density profile that gives the
least mixing Evaluate both:
– maxium stratification (largest differential in sigma-t values)
– minimum stratification (smallest differential in sigma-t values)
Human Health– Use average of maximum and minimum
![Page 24: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/24.jpg)
Dilution Type Unidirectional flow:
– Acute and Chronic …… Centerline– Human Health …… flux average
Marine and rotating flows: – Acute and Chronic/ …… Flux average
Human Health
![Page 25: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/25.jpg)
Overlapping Mixing Zones
Allowed where: Combined size meets the maximum mixing
zone size limitations
No barrier to migration of indigenous organisms with potential for ecosystem damage
![Page 26: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/26.jpg)
EXTENDED MIXING ZONES
May be considered for: Discharges existing prior to 1992 Where altering the size increases
protection Where volume of effluent is more
beneficial than removing the discharge.
Necessary for social or economic development in the area.
![Page 27: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/27.jpg)
Mixing zones for Stormwater
Maybe granted exemption from size limitations if:
All BMP’S have been applied No potential threat to
– Sensitive habitat and ecosystem– Public health– Beneficial uses
No barrier to migration of indigenous organisms with potential for ecosystem damage
![Page 28: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/28.jpg)
Mixing zones for CSO’s• Must comply with all mixing zone
requirements• But, exempt from size criteria once a
year provided “no environmental harm” clause is fulfilled
![Page 29: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/29.jpg)
UM3• Simulates 3D plume trajectory• Predicts centerline based on 3/2 power
(~gaussian) profile and top-hat (average) concentrations
• Multiport plume merging simulated with reflection technique
• Does not directly resolve lateral or bottom boundary constraints
![Page 30: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/30.jpg)
VSW Same as UM3 but applied to very shallow
waters Resolves bottom constraint (bottom hit)
by reflection technique
![Page 31: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/31.jpg)
RSB….”range of experiment” Straight diffuser, uniformly spaced round ports on
T-risers, horizontal ports in marine waters with plumes merging rapidly with length scale ratios:
5.0078.0 b
m
ll
92.131.0 bls
S = port spacing; lb = relates buoyancy per unit diffuser length to brunt Vaisala density frequency; lm = relates momentum to density per unit length
Diffuser pipe T-riser
ports
![Page 32: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/32.jpg)
CORMIX CORMIX 1 single port positive/neutral buoyant
discharges CORMIX 2 multiport positive/neutral
buoyant discharges Uses “equivalent slot diffuser” May need CORMIX1 if plume details near each
port are desired CORMIX 3 buoyant surface discharge
![Page 33: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/33.jpg)
RIVPLUME (based on Fischer et al. 1979) Single port, short diffuser, or bank discharge
Plume completely and rapidly vertically mixed within the acute zone. So a 2-D model
Uses mean cross-sectional velocity
It incorporates boundary effects of shoreline through superposition
Cannot model ambient density stratification, dense plumes or tidal buildup
Available at the following site:http://
www.ecy.wa.gov/programs/eap/pwspread/pwspread.html
![Page 34: Instantaneous snapshot](https://reader033.vdocument.in/reader033/viewer/2022061610/568163fe550346895dd59c51/html5/thumbnails/34.jpg)
CFD (Computational Fluid Dynamics)
Mesh = 2.5 million grid cells (600 ft by 300 ft)
Courtesy: Dr. Lin Fangbiao, Stantec Corporation